If you take part in this research study, you will be given a study drug-dosing calendar for each treatment cycle. There will be a 14 day lead in phase of BKM120 alone to assess for toxicity from this agent. After the lead in phase, the standard dose of abiraterone and prednisone will be added to the BKM120 treatment regimen. Treatment cycles will last 4 weeks (28 days), during which time you will be taking the study drug in combination with the standard drug therapy once daily. Your time of participation in the study will be based on how well you tolerate the experimental drug. You could be participating in the study for a period of days, or years, depending on the course of your cancer.